C. Battery Charge Limiter Functions The functions of battery charge limiter are as follows:
(1) Control of the battery contactor:
-
to ensure battery charge,
-
to start or assist starting of the APU,
-
to protect the battery against thermal runaway or short circuit,
-
to control equipment DC supply on ground, when no normal power is available,
-
to prevent complete discharge of the battery, when the aircraft is parked,
-
to supply equipment with DC during transient fault configurations,
-
to ensure integrity of the HOT bus.
(a) Battery charge When battery voltage is lower than 26.5 V, beginning of the charging cycle. When battery charge current is lower than 4 A, end of the charging cycle.
NOTE : In flight or following APU start, when the battery charge
____ current is lower than 4 A, a 30 mn time delay in the BCL controls the end of the charging cycle.
(b)
Thermal runaway and internal short circuit
Battery isolation occurs in case of:
-
charge current increasing with a slope greater than 0.375 A/mn.
-
charge current greater than a threshold (150 A) during 1 minute and 30 seconds.
(c)
Starting of the APU When the APU start sequence is initiated, the two batteries are connected to 28 VDC BAT BUS (3PP) to supply the APU starter motor.
(d)
Supply on ground When IDG's, APU generator or external power are not available on ground, the batteries supply:
-
the 28 VDC BAT BUS (3PP) through the contactors 6PB1 and 6PB2,
-
the 28 VDC ESS BUS (4PP) through the contactor 2XB,
-
the 115 VAC STAT INV BUS (901XP) through the static inverter
3XB. (the BAT1(2) pushbutton switches are pushed).
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(e) Protection against complete discharge On ground, the batteries are automatically disconnected from the DC network when battery voltage is lower than 23 V during 15 seconds.
NOTE : But the disconnected battery always supplies its related
____
HOT bus.
(f)
Transient fault conditions Battery contactors are closed during 7 seconds when DC network is lost.
(g)
Integrity of the HOT bus Battery isolation in case of failure on DC network through monitoring of the battery discharge current (either I discharge > 400 A for 5 ms or I discharge > 100 A for 300 ms).
(h)
Electrical emergency event Battery isolation in case of AC normal busbars failure (loss of AC main generation) except when APU start sequence is initiated.
(2)
RAT & EMER GEN control In case of AC normal busbars failure (loss of AC main generation) the red FAULT legend of the RAT & EMER GEN pushbutton switch on the ELEC EMER PWR section of the overhead panel 21VU comes on until the emergency generator is available (operational). The FAULT legend is inhibited when the landing gear is compressed.
(3)
Inhibition of the APU start sequence In flight, when the electrical emergency configuration is initiated, the APU start sequence is inhibited during 45 seconds.
NOTE : If the CSM/G comes on line before 45 seconds, the APU start
____ sequence is available as soon as the CSM/G is coupled to the network.
(4) BAT - Fault warning control When a thermal runaway occurs the FAULT legend of the BAT1(2) pushbutton switch comes on on the overhead ELEC panel 35VU. The battery contactors are opened but no action is required from the crew.
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R **ON A/C ALL
5. BITE Test
_________
Built-In Test Equipment (BITE) allows two types of test:
-
tests at each power up on ground,
-
tests on ground from the Centralized Fault Display System (CFDS).
Furthermore, the BCL system is monitored when the BCL is in operation.
A.
Power up Test On the ground, when the equipment is switched on, the following tests are performed:
-EPROM test (checksum),
-RAM test,
-timer test,
-discret inputs test,
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